关键词: 糙米 , 储藏 , &gamma, 辐照 , 结构 , 糊化特性 , 直链淀粉

Abstract: 【Objective】 China is a big consumer of grain, grain storage relates to national security and social stability. Irradiation is used in many areas, such as food storage and processing and so on. This paper conducted with clarify the change mechanisms of rice quality dealt with 60Co gamma irradiation by cooking and texture quality changes of storaging brown rice. The purpose of this study is to determine the suitable irradiation dose, provide a theoretical basis for determining applicable gamma irradiation dose and technical methods of storaging brown rice. 【Method】 After harvest, the grains were peeled, filled into the plastic film bags, and then irradiated with 60Co gamma at irradiation doses of 0.2 kGy, 0.5 kGy, 1.0 kGy and 2.0 kGy. After measuring the initial index of brown rice, the rice samples were stored at (15 ± 0.5 ℃) for one year, the quality of brown rice was measured every three months: amylose content was determined by amylose instrument, gelatinization parameters were determined by using the RNA viscosity instrument, construction quality of rice was measured by properties instrument, microstructure of irradiated rice starch granules were observed with scanning electron microscope.【Result】 In this study, we can conclude the following results. It was found that rice pasting peak viscosity increased with prolonged storage time, the increasing trends were different among different doses, through viscosity and breakdown value increased with prolonged storage time. Gamma irradiation reduced through viscosity, final viscosity, setback value and breakdown value of brown rice. Pasting temperature increased with the irradiation dose, the higher the pasting temperature, the more the brown rice resists to cooking, the higher the quality obtained. Gamma irradiation affected the setback value and final viscosity of brown rice mostly, and 0.2 kGy dose irradiation could increase the stability of cold rice paste and improve cooking quality significantly (P＜0.05), the change trend of final viscosity was similar to setback value. Amylose content of brown rice increased with storage time, after gamma irradiation ,the amylose content increased. For brown rice of low apparent amylose content ,the cooking hardness and amylose content showed no obvious correlation (P＞0.05). During the one year storage, the cooking hardness increased with time, however, gamma irradiation decreased the hardness of brown rice, the hardness of brown rice irradiated at 0.5 kGy and above showed a difference with non-irradiation rice significantly (P＜0.05). Irradiation coule prolong the decline of adhesive property of cooking rice, as a result, 0.5 kGy of irradiation improved the quality of stored cooking brown rice. Irradiation modified the structure and morphology of starch granules, the space between starch granules became larger after irradiation, more water could be penetrated when cooking, so the quality of the cooking brown rice improved.【Conclusion】 Gamma-irradiation changed the starch granule morphology and structure of stored brown rice, improved the quality and texture of cooked rice irradiated during storage at the doses from 0.5 kGy to 2.0 kGy.

Key words: brown rice , storage , gamma irradiation , structure , pasting properties , amylose